Vibrating sensors, such as for example, vibrating densitometers and Coriolis flowmeters are generally known, and are used to measure mass flow and other information for materials flowing through a conduit in the flowmeter. Exemplary Coriolis flowmeters are disclosed in U.S. Pat. Nos. 4,109,524, 4,491,025, and Re. 31,450, all to J. E. Smith et al. These flowmeters have one or more conduits of a straight or curved configuration. Each conduit configuration in a Coriolis mass flowmeter, for example, has a set of natural vibration modes, which may be of simple bending, torsional, or coupled type. Each conduit can be driven to oscillate at a preferred mode.
Some types of mass flowmeters, especially Coriolis flowmeters, are capable of being operated in a manner that performs a direct measurement of density to provide volumetric information through the quotient of mass over density. See, e.g., U.S. Pat. No. 4,872,351 to Ruesch for a net oil computer that uses a Coriolis flowmeter to measure the density of an unknown multiphase fluid. U.S. Pat. No. 5,687,100 to Buttler et al. teaches a Coriolis effect densitometer that corrects the density readings for mass flow rate effects in a mass flowmeter operating as a vibrating tube densitometer.
Material flows into the flowmeter from a connected pipeline on the inlet side of the flowmeter, is directed through the conduit(s), and exits the flowmeter through the outlet side of the flowmeter. The natural vibration modes of the vibrating system are defined in part by the combined mass of the conduits and the material flowing within the conduits.
When there is no flow through the flowmeter, a driving force applied to the conduit(s) causes all points along the conduit(s) to oscillate with identical phase or a small “zero offset”, which is a time delay measured at zero flow. As material begins to flow through the flowmeter, Coriolis forces cause each point along the conduit(s) to have a different phase. For example, the phase at the inlet end of the flowmeter lags the phase at the centralized driver position, while the phase at the outlet leads the phase at the centralized driver position. Pickoffs on the conduit(s) produce sinusoidal signals representative of the motion of the conduit(s). Signals output from the pickoffs are processed to determine the time delay between the pickoffs. The time delay between the two or more pickoffs is proportional to the mass flow rate of material flowing through the conduit(s).
Meter electronics connected to the driver generate a drive signal to operate the driver and determine a mass flow rate and other properties of a material from signals received from the pickoffs. The driver may comprise one of many well known arrangements; however, a magnet and an opposing drive coil have received great success in the flowmeter industry. An alternating current is passed to the drive coil for vibrating the conduit(s) at a desired conduit amplitude and frequency. It is also known in the art to provide the pickoffs as a magnet and coil arrangement very similar to the driver arrangement. However, while the driver receives a current which induces a motion, the pickoffs can use the motion provided by the driver to induce a voltage. The magnitude of the time delay measured by the pickoffs is very small; often measured in nanoseconds. Therefore, it is necessary to have the transducer output be very accurate.
In certain situations, it is desirable to incorporate multiple flowmeters in a single system. In one such multi-flowmeter example, two flowmeters may be employed in large engine fuel systems. Such systems are commonly found in large seafaring vessels. For such vessels, proper fuel management is critical for efficient engine system operation. To accurately measure fuel consumption, a flowmeter is placed upstream of the engine and another flowmeter is placed downstream of the engine. The differential reading between the two flowmeters is used to calculate the mass of fuel consumed.
A flowmeter of a given size requires a certain fluid flow range to maintain accuracy. On the other hand, a given system may have a range of fluid flow requirements, thus necessitating a flowmeter that does not unduly restrict the system's operation. The best flowmeter for a particular system is therefore one that measures flow and related parameters accurately, yet does not restrict flow or introduce burdensome pressure drops. When two flowmeters are in a single system, flow restriction and accuracy issues are magnified. For example, a pair of flowmeters having 0.1% accuracy errors, when placed in series may not simply add up to be a 0.2% error, but may be far larger. Temperature differentials and zero-stability differentials between two or more flowmeters also contribute to lower system accuracy.
Therefore, there is a need in the art for a method and related system to calculate the most appropriate sizes and types of flowmeters in multi-flowmeter systems based upon a set of given operating constraints. There is a need for a method and related system to determine multi-flowmeter system accuracy. There is a need for a method and related system to determine particular flowmeter models from a library of candidate flowmeters in light of project requirements. The present invention overcomes these and other problems and an advance in the art is achieved.